Abstract
BackgroundEstimation of the dietary requirements for vitamin D is crucial from a public health perspective in providing a framework for the prevention of vitamin D deficiency. It has been shown that pooling individual participant-level data (IPD) from selected randomised controlled trials (RCTs) of white children and adults facilitated the generation of more accurate estimates of the vitamin D requirement. Recent RCT data suggest the vitamin D requirement of dark-skinned, particularly black, individuals, an at-risk group of vitamin D deficiency, is greater than those of white counterparts. Thus, we wished to develop a study protocol for the conduct of an IPD-level meta-analysis of vitamin D requirements using data from appropriate vitamin D RCTs in dark-skinned population subgroups.MethodsThe study protocol details the steps needed within such an IPD meta-analysis which will include its registration, constituent systematic review to identify all appropriate RCTs on the basis of pre-specified eligibility criteria, the associated data collection, handling, and synthesis, as well as checking the integrity of the IPD, followed by implementation of a one/two-stage IPD meta-analysis and derivation of vitamin D requirement estimates.DiscussionAs dark-skinned population subgroups are at increased risk of vitamin D deficiency, further investigation of dietary recommendations for vitamin D in these subgroups is needed. We strongly believe that application of an IPD-based meta-analysis is a highly strategic approach by which to undertake some of this further investigation. Such IPD-based analysis, however, will need collaboration across the principal investigators of the identified RCTs meeting with the eligibility criteria, and the availability of this study protocol will be important to highlight the potential of IPD-based analysis for estimation of the dietary requirement for vitamin D for this particular population subgroup as well as for other at-risk target populations.Systematic review registrationPROSPERO International Prospective Register of Systematic Reviews (registration number: CRD42018092343).
Highlights
Estimation of the dietary requirements for vitamin D is crucial from a public health perspective in providing a framework for the prevention of vitamin D deficiency
We have provided randomised controlled trials (RCTs) data to suggest that calcium intake does not influence the response of serum 25(OH)D to vitamin D supplementation [32] and Dietary Reference Values (DRVs) for vitamin D are established under the assumption that calcium intake is adequate [2,3,4, 14]
In light of recent findings showing that dark-skinned population subgroups are at increased risk of vitamin D deficiency [6,7,8], a more comprehensive investigation of dietary recommendations for vitamin D in these subgroups is much needed
Summary
The study protocol details the steps needed within such an IPD meta-analysis which will include its registration, constituent systematic review to identify all appropriate RCTs on the basis of pre-specified eligibility criteria, the associated data collection, handling, and synthesis, as well as checking the integrity of the IPD, followed by implementation of a one/two-stage IPD meta-analysis and derivation of vitamin D requirement estimates
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